Hitherto, there exists an air-conditioning system including a heat pump unit that performs indoor heating using a vapor-compression refrigeration cycle and an other heat source unit that performs indoor heating using a heat source different from a heat source of the heat pump unit. As the air-conditioning system described above, the following technology has been proposed. Specifically, when there is satisfied a first switching condition that an outside air temperature reaches a first switching outside air temperature and a heating capacity of the heat pump unit reaches an upper limit during a period in which a heat pump heating operation is being performed, the heat pump heating operation is switched to an other heat source heating operation for performing indoor heating using the other heat source unit (see, for example, Japanese Unexamined Patent Application Publication No. 2015-145759).